Novel interpolymers useful as thickening agents

ABSTRACT

Interpolymers consisting essentially of the structural units in anhydride form:   WHEREIN X represents -O-; Y represents -OH, -OR1, and when Y and R2 are taken together represent a single bond of an imide ring; R1 and R2 represent hydrogen or the same or different hydrocarbon radicals having from one to 50 carbon atoms and together contain a total of from six to 50 carbon atoms selected from the group consisting of normal chain alkyl, branched chain alkyl, cycloalkyl, and alkylaryl radicals; (WHERE X -O-, R2 does not exist); R3 represents the same or different hydrocarbon radicals selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and CH2CH2O)q(CH2)mCH3 radicals wherein q represents an integer of from about 1 to about 3 and m represents an integer of from about 0 to about 3.

United States Patent Field et a].

1 1 NOVEL INTERPOLYMERS USEFUL AS THICKENING AGENTS [72] Inventors:Nathan D. Field, 2736 Liberty St.,

Allentown, Pa. 18104; Earl P. Willians, 803 Applegate Ave., Pen Argyl,Pa. 18072 [22] Filed: March 20, 1970 [2]] Appl. N0.: 21,476

[52] US. Cl. ..260/78.5 T, 71/1, 167/87, 167/87.1, 167/91, 260/29.1 R,260/29.2 R, 260/29.6 RB, 260/30.2, 260/30.6 R, 260/32.6 N, 260/33.4 PQ,260/78 UA [511 IntICI. ..C08f 27/12 [58] Field of Search ..260/78.5 T

[56] References Cited UNITED STATES PATENTS 2,985,625 5/1961 Jones..260/78 2,866,772 12/1958 Sellers ..260/45.7 3,398,092 8/1968 Field atal ..210/24 2,977,334 3/1961 Zopf et a1. ..260/27 2,698,316 12/1954Giammaria ..260/78 3,506,625 4/1970 Patinkin et a1 ..260/785 3,499,8763/1970 Field et a1 ..260/78.5

Primary Examiner-Joseph L. Schofer Assistant Examiner-John Kight, III

Attorney-Samson B. Leavitt, Walter C. Kehm and Alvin H. F ritschler [57]ABSTRACT lnterpolymers consisting essentially of the struetural I [1 13,684,776 [451 Aug. 15, 1972 units in anliydride form:

UNIT 1 UNIT 1r -CHCHz-CHCH- I l --oncmolrcu- 0:0 0:0 and l l 0 =0 (120R3 0 I l l n Y \-m wherein X represents Y represents -OH, OR,,

and when Y and R, are taken together represent a single bond of an imidering; R and R, represent 'cili'fifivlllirglfi 3%??? o18228$23$$ L'rcontain a total of from six to 50 carbon atoms selected from the groupconsisting of normal chain alkyl, branched chain alkyl, cycloalkyl, andalkylaryl radicals; (where X -O-, R, does not exist); R represents thesame or different hydrocarbon radicals selected from the groupconsisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl,and{-CI-I CH O),(CH CH radicals wherein 0 represents an integer of fromabout 1 to about 3 and m represents an integer of from about 91. smu,3.-

5 Claims, No Drawings The instant invention is directed to novelinterpolymer compositions. In particular, the instant invention isdirected to novel interpolymer compositions which are useful asthickening agent.

We have now discovered a new class of highly useful interpolymers thatare derivatives of maleic anhydride and a vinyl ether monomer ormixtures of vinyl ether monomers which may be used as thickening agents.

The instant compounds have been found to be very useful in thickeningsolutions of high ionic strength, including concentrated salt solutionsas well as bases and acids where most conventional water-solublepolymers have little effect or are insoluble. For example, the instantinterpolymers are very effective in thickening 15 percent diammoniumphosphate solution, which is used in fire-fighting and 20 percenttetrapotassium pyrophosphate which is used in detergent compositions andpercent sodium bromate which is used in permanent wave formulations.Moreover, the instant interpolymers are very effective for thickeningconcentrated ammonia as well as for thickening other strong alkalisolutions such as sodium hydroxide, sodium carbonate, trisodiumphosphate and sodium silicate. The thickened ammonia solutions areuseful as agricultural fertilizers and the thickened strongly alkalinesolutions are useful as heavy duty cleaners, pain removers, ovencleaners, etc. Moreover, the instant compounds may be used to thickenwater and rubber latices as well as nonaqueous solutions or mixtures ofnon-aqueous and aqueous solutions such as glycerine, ethylene glycol,alcohols, methyl ethyl ketone, acetone, dimethyl formamide, dioxane aswell as water solutionsof the above. The instant compounds are alsouseful as gelling agents in cosmetic formulations such as shampoos, handtions, shaving creams, etc. The above solutions and dispersions havegood stability upon storage, in fact some of them have even exhibitedincreased viscosity values upon storage.

The vinyl monomers which may be employed in connection with the instantinvention may be represented by the structural formula:

wherein R represents the same or different hydrocarbon radicals selectedfrom the group consisting of methyl, ethyl, propyl, isopropyl, butyl,isobutyl and (CH CH O), (CH ),,,CH radicals wherein q represents aninteger from about 1 to about 3 and m represents an integer of fromabout 0 to about 3.

More specifically, the novel interpolymers of the instant invention arethose which have the following structural units:

wherein Xrepresents N -O-;

R1 Y represents -OH, -OR -X and when Y and R are taken togetherrepresent a single bond of an imide ring; R and R represent hydrogen orthe same ordifferent hydrocarbon radicals having from 1 50 carbon atomsand together contain a total of from 6 to 50 carbon atoms selected fromthe group consisting of normal chain alkyl, branched chain alkyl,cycloalkyl, and alkylaryl radicals (where X=0 R does not exist); Rrepresents the same or different hydrocarbon radicals selected from thegroup consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl,and {CH CH O),,(CH ),,,CH radicals wherein q represents an integer offrom about 1 to about 3 m represents an integer of from about 0 to about3.

Wherein structural Unit 1 represents about to 99.5 mole percent andstructural Unit H represents about 25 to 0.5 mole percent of theinterpolymer preferably about to 99 mole percent in Unit I and about 1to 15 mole percent in Unit II.

The molecular weight of the novel interpolymers of this invention may beconveniently defined by way of the specific viscosity of the precursorcopolymer. That is to say, the molecular weight may be defined by thespecific viscosity of Units I and Ill wherein both units are totallyanhydride units prior to amidation or esterification of Unit [1. In suchinstances one gram of the copolymer per 100 milliliters of methyl ethylketone solution should have a specific viscosity of 25 C in the range offrom about 0.1 to about 25.0 Preferably, the novel interpolymers of theinstant invention have a specific viscosity at 25 C in methyl ethylketone solution of from about 0.2 to about 20.

The partial ester, amide or imide interpolymers of the instant inventionmay be prepared in two steps via conventional known methods. Forexample, the precursor anhydride copolymers are well known in the artand may be prepared by interpolymerizing maleic anhydride and a vinylether monomer or mixtures of vinyl ether monomers using approximatelyone mole of maleic anhydride per mole of vinyl ether monomer. A smallmolar excess of the vinyl ether monomer (5 to [0 percent) above that ofthe maleic anhydride may be advantageous for insuring completeconversion of the maleic anhydride. The polymerization is carried outconveniently by preparing a solvent solution of the monomers with acatalytic amount (preferably from 0.01 to 1.0 percent) of an organicfree-radical-generating initiator. The resulting solution is mixedthoroughly and heated sufficiently so that polymerization reaction takesplace. The amount of solvent is not critical and such solvents asbenzene, toluene, xylene, acetone, methyl ethyl ketone, and methylenechloride, and the like may be used. However, benzene is considered themost suitable from the standpoint of product isolation and obtaininghigh molecular weights. The resultant anhydride copolymer slurry maythen be employed as is or diluted with additional or different solventsor isolated by any suitable means, such as filtration and reslurried ordissolved in a more suitable solvent for the subsequent esterificationor amidation or imidation reaction.

Among the organic free-radical-generating initiators that may bementioned are azobisisobutyronitrile, benzoyl peroxide, lauroylperoxide, caprylyl peroxide, acetyl peroxide, acetyl benzoyl peroxide,di-tert-butyl peroxide or dimethyl azoisobutyrate and the like. Mixturesof such catalysts are also suitable in the process of making theinterpolymers of the invention. Radiation polymerization can be used,too, e.g., such high energy radiation sources as ultra violet light,X-rays, y -rays, neutrons and the like can be used to initiatepolymerization.

The polymerization may be carried out at a temperature within the rangeof to 150, preferred temperatures lie for the most part in the rangefrom 40 to 100 C., particularly about 6080 C.

Among the vinyl ether monomers represented by R OCl-l CH suitable foruse are methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether,isopropyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether,methoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, and themonomethyl ether of triethylene glycol vinyl ether or mixtures thereof.

The second step of the preparation of the novel interpolymers of theinstant invention is the reaction of the resultant copolymer of theprocess set forth above so as to form the partial amide or partial esteror partial imide thereof. The partial amide may be prepared by reactionof said copolymer with a monoamino primary or secondary amine containingfrom about six to about 50 carbon atoms in molar amounts of from about0.5 to about 25 percent of the total anhydride content. Conditions forthe formation of the subject amides are well known in the art andinclude the reaction of the abovenoted amines with the anhydridecopolymer in a suitable solvent therefor for a suitable period of time.Amines which may be employed to prepare the partial amides of theinstant invention may be exemplified by the following:

hexyl amine heptyl amine octyl amine nonyl amine decyl amine hendecylamine dodecyl amine tetradecyl amine hexadecyl amine octadecyl amineoleylamine stearyl amine octadecadienylamine 2-aminooctane tertiarynonylamine coconut fatty amine soya fatty amine tallow fatty aminehydrogenated tallow fatty amine tall oil amine rosin aminecyclohexylamine benzylamine di-n-propylamine di-iso-propylaminedibutylamine diamylamine didodecylamine dioctadecylamine tridecylamine2-ethylhexyl amine di( 2-ethylhexyl)amine N-methyl dodecylamine N-ethyltetradecylamine iso-decyl amine and mixtures of such amines in anyproportions.

The partial ester interpolymers of the instant invention may be preparedby reaction of the abovediscussed anhydride copolymers with a monohydrichydrophobic alcohol containing from about six to about 36 carbon atomsin molar amounts of from about 0.5 to 25 percent of the total anhydridecontent. The conditions for such formation are all well known in the artand, therefore, not set forth herein in detail. Exemplary of thealcohols which may be employed in connection with the instant inventionare the following:

n-hexanol n-heptanol n-octanol n-nonanol n-decanol n-dodecanoln-tetradecanol n-hexadecanol n-octadecanol oleyl alcohol branchedchained alcohols such as sec octanol pentamethyloctanoltetramethylnonanol diethyloctanol.

Furthermore, alcohols prepared by the catalytic reaction of an olefinsuch as tripropylene, tetrapropylene, pentapropylene, and the like withcarbon monoxide and hydrogen to form an aldehyde followed by thecatalytic reduction of said aldehyde to an alcohol may also be employed.The above process for the production of such alcohols is known as theoxo process. Furthermore, alcohols such as cyclohexanol, a-terpineol,cholesterol, benzyl alcohol, B-phenylethyl alcohol, cinnamyl alcohol,citronellol and the like, as well as mixtures of any of the above suchas Lorol 5 which is a mixture of C to C alcohols.

The partial imides of the subject invention may be prepared byconverting all or part of the partial amides formed according to theabove to imide under conditions as are set forth in U. S. Pat. No.2,313,565 which is hereby incorporated by reference. That is to say,that the above formed amide may be reacted in a methylated naphthalenefor a period of from 0.5 to 5 hours at temperatures of from about to 250so as to convert the amide to the imide form. The resultant product isthen cooled, filtered and washed with a suitable sol vent and filteredand dried.

. um hydroxide,

The anhydride interpolymers of this invention may be converted byhydrolysis, neutralization, esterification and the like to compoundshaving the following structural units:

UNIT UNIT II wherein X, Y, R,, R and R and the mole percentages of UnitI and Unit II have the same meaning as described, and wherein A' and Beach independently represent a member selected from the group consistingof --OH, OM, --NH alkoxy, and aryloxy, where Z, and Z, are selected fromthe group consisting of hydrogen, alkyl, aryl or together from a ring,and wherein M represents a salt forming cation selected from the groupconsisting of alkali metals, ammonium and substituted ammonium, such asK, Na, NH,,, methylammonium, diethanolarnmonium, piperidinium,morpholinium, triethanolammonium and the like.

- The above water-soluble interpolymers include those ammoniatedproducts involving partial as well as complete conversion of theanhydride moiety such as those compounds containing the ammoniumsalt-half amide moiety which may be depicted as:

These water-soluble interpolymers may be easily derived from theabove-described interpolymers by forming derivatives of the anhydrideportion of the polymer, by known hydrolyzing reaction thereof withwater, and/or reactions involving primary and secondary alcohols,primary and secondary amines or alkali basic media to form salts,partial ester-salts, or partial amide-salts and the like.

Among the more preferred reactants that may be mentioned are water,ammonia, alkali solutions, such as sodium hydroxide, potassium hydroxideor ammonietc.; methylarnine, piperidine, morpholine, diethanolamine,triethanolamine, etc.; alcohols, such as methanol, ethanol, propanol,and the like; phenols, naphthols, etc.

As noted, an object of the instant invention is to provide novelinterpolymers which are particularly useful in thickened aqueoussystems, i.e., in a composition of matter comprising an aqueous systemhaving therein a thickening amount of the novel interpolymers of theinstant invention.

Such systems include, for example, water itself, aqueous-alkalinemixtures, aqueous-alcohol mixtures, aqueous-acid systems, aqueous ionicsalt mixtures, polymer latices, and the like. Examples of the aqueousionic salt, acid or alkali systems which can be thickened in accordancewith present invention include solutions of diammonium phosphate,tetrapotassium pyrophosphate, ammonium hydroxide, tetrapotassiumpyrophosphate, ammonium hydroxide, sodium hydroxide, sodium bromate,hydrochloric acid, and the like.

The amount of water present in the above-mentioned aqueous systems is inno way critical, as the thickeners employed can be utilized to thickencompositions wherein water is present in only a minor amount up to anaqueous system where water is the major component. The amount of waterpresent in the aqueous system, therefor, is merely dependent on the usefor which the thickened system is intended. In general, however, it ispreferred to utilize aqueous solutions containing 1 to percent ionicmaterial.

Furthermore, the amount of thickener to be employed in the aqueouscompositions will vary according to the desired result, the systememployed, and as a practical matter, the general economicconsiderations. In general, however, a range of from about 0.1 to about15 percent by weight of the total aqueous composition is employed,although greater or lesser amounts can be advantageously employed whendesired.

The use of the instant thickeners in the above aqueous systems is indeedunique. For example, in many ionic solutions using standard thickenersthe viscosity decreases as the ionic content increases. Hence, it wasunexpected that the viscosity increased with ionic content when usingthe novel subject thickeners.

The following examples are illustrative of the present invention and arenot to be regarded as limitative. It is to be understood that all parts,percentages and pro portions referred to herein and in the appendedclaims are by weight unless otherwise indicated. The viscosities listedin the following examples were obtained with a Brookfield rotationviscometer and the value expressed in centipoises. The designationPVM/MA" as used in this example and in the following examples, is thecommonly abbreviated form for methyl vinyl ethermaleic anhydridecopolymer.

EXAMPLE 1 The following solution was prepared:

31.2 grams (0.2 moles of PVM/MA, specific viscosity 1 percent in methylethyl ketone at 25 C 3.47) was dissolved in 1,000 ml. C. P. methyl ethylketone in a 2-liter reaction flask equipped with stirrer, refluxcondenser and thermometer. To this was added 2.4 g (0.008 mole)hydrogenated tallow fatty amine (a mix ture of 25 percent hexadecylamine, percent octadecyl amine, and 5 percent octadecenyl amine)dissolved in 40 ml. of C. P. methyl ethyl ketone.

The solution was then stirred for 19 hours at from about 25 to 28 C andthen poured into 3,300 ml. of nheptane filtered and then dried in avacuum oven at 25 C. The dried product 4 mole percent hydrogenatedtallow amide of PVM/MA weighed 33.0 grams.

EXAMPLE 2 7.8 gr'ams(0.05 moles) of the PVM/MA used in Example l wasdissolved in 200 mls. of C. P. methyl ethyl ketone in a 500 ml. reactionflask equipped with stirrer, reflux condensor and thermometer. To thiswas added 1.0 g of cetyl alcohol (0.004 moles) dissolved in 10 ml of C.P. methyl ethyl ketone. The mixture was then heated to reflux at 77 Cand held to this temperature for approximately 16 hours. The solutionwas then cooled to 25 C and poured into 1,200 ml. n-heptane, filtered,and dried in a vacuum oven at 25C. The dried powder of 8.0 mole percentcetyl ester of PVM/MA weight 8.0 grams.

EXAMPLE 3 5.0 grams of the product of Example 1 were heated EXAMPLE 4The thickening properties of the subject polyamide interpolymers weredemonstrated as follows. A solution of:

interpolymer Example 1 1.00 g. Diammonium phosphate 15.0 g. Distilledwater 84.0 g.

was prepared. The mixture was rotated on a vertically mounted slowlyrevolving (3.5 rpm) 30 inch diameter wheel for a period of 18 hours at25 C. The polymer solution exhibited a Brookfield viscosity of 3,200 CPSat 25 C using a No. 7 spindle and 10 rpm.

EXAMPLE 5 A 2 percent interpolymer solution was prepared to demonstratethe thickening qualities of the subject interpolymers. A solution of:

interpolymer Example 1 2.0 g. Diammonium phosphate 15.0 g. Distilledwater 83.0 g.

was prepared. The mixture was rotated on a vertically mounted slowlyrevolving (3.5 rpm) 30 inch diameter wheel for a'period of 18 hours at25 C. The polymer solution exhibited a Brookfield viscosity of 64,000CPS at 25 C using a No. 7 spindle and rpm.

EXAMPLE 6 So as to compare the effects of the novel interpolymers of theinstant invention with PVM/MA alone the following solution was prepared:

PVM/MA of Example 1 Diammonium phosphate 15.0 g. Distilled water 84.0 g.

was prepared. The mixture was treated as in Example 4 and found to havea Brookfield viscosity of 52 CPS at C using a No. 3 spindle and 10 rpm.This comparison clearly evidences the novel and unexpected resultsobtained by the subject interpolymers of the instant invention.

EXAMPLE 7 As a comparison to Example 5, a 2 percent polymer solution ofPVM/MA was prepared.

PVM/MA of Example 1 Diammonium phosphate 2.0 15 .0 Distilled water 83.0

manor:

EXAMPLE 8 Four grams of an interpolymer prepared according to Example 2,comprising 1 mole of PVM/MA as in Example l reacted with 0.08 moles ofcetyl alcohol were mixed with 15.0 grams of diammonium phosphate and81.0 grams of distilled water. The mixture was rotated as in Example 4and found to have a Brookfield viscosity of 32,400 CPS at 25 C using aNo. 7 spindle and 10 rpm.

For comparative purposes, 4 grams of the PVM/MA copolymer used inExample 1 was mixed with 15.0 grams of diammonium phosphate and 81.0grams of distilled water. The mixture was rotated as in Example 4 andfound to have a Brookfield viscosity of 800 CPS at 25 C using a No. 7spindle and 10 rpm.

EXAMPLE 9 One gram of an interpolymer prepared according to Example 1were mixed with 47.0 grams of distilled water, 52.0 grams of 28.9percent ammonia solution. The mixture was rotated as in Example 4 andfound to have a Brookfield viscosity of 46,400 CPS at 25 C using a No. 7spindle at 10 rpm.

The above procedure was repeated employing PVM/MA in lieu of theinterpolymer of the instant invention. The resultant solution was foundto have a Brookfield viscosity of 450 CPS at 25 C using a No. 6 spindleand 10 rpm.

EXAMPLE 10 Two grams of an interpolymer comprising isobutylvinyl etherand maleic anhydride copolymer (specific viscosity 1 percent methylethyl ketone 2.7 at 25 C) reacted with hydrogenated tallow fatty amine,were prepared as in Example 1. The interpolymer was mixed with 46.0grams of distilled water and 52.0 grams of 28.9 percent ammoniasolution. The mixture was treated as in Example 4 and found to have aBrookfield viscosity of 142,000 CPS at 25 C using a No. 7 spindle and 10rpm. the exception that the unmodified copolymer of isobutylvinyl etherand maleic anhydride was substituted for the novel interpolymer of theinstant invention. The resultant mixture was found to have a Brookfieldviscosity of 608 CPS at 25 C using a No. 5 spindle and 10 rpm.

EXAMPLE 1 l A mixture was prepared using 1 gram of the interpolymer ofExample 1 in combination with 79.0 grams distilled water and 5.0 gramsof tetrapotassium pyrophosphate. The mixture was treated as in Example 4and found to have a Brookfield viscosity of 5,600 CPS at 25 C using aNo. 7 spindle and 10 rpm.

For purposes of comparison, the above mixture was prepared employing acopolymer of PVM/MA as in Example l in lieu of the novel interpolymer ofthe instant invention. The resultant mixture was found to have aBrookfield viscosity of 35 CPS at 25 C using a No. 3 spindle and 10 rpm.

EXAMPLE 12 One gram of the interpolymer of Example 1 was mixed with 5.0grams of sodium bromate, 92.3 grams distilled water and 1.7 grams 15percent (w/w) sodium hydroxide solution. The mixture was treated as inExample 4 for a period .of 65 hours. The mixture was found to have aBrookfield viscosity of 3,840 CPS at 25 C using a No. 7 spindle and 10rpm. For purposes of comparison, the above composition was preparedusing the unmodified copolymer of PVM/MA of Example 1 in lieu of thenovel interpolymer of the instant invention. The resultant mixture wasfound to have a Brookfield viscosity of 20 CPS at 25 C using a No. 3 and10 rpm.

EXAMPLE 13 One gram of the interpolymer of Example 1 was mixed with 46.5grams of distilled water, 1.4 grams percent (w/w) sodium hydroxidesolution. 2.5 grams of sodium chloride was then added to the mixture andsaid mixture was treated as in Example 4. The mixture was found to have.a Brookfield viscosity of 2,000 CPS at 25 C using a No. 6 spindle and 10rpm.

For purposes of comparison, the above mixture was again preparedemploying the unmodified PVM/MA copolymer of Example 1 in lieu of thenovel interpolymer of the instant invention. The mixture was found tohave a Brookfield viscosity of 95 CPS at 25 C using a No. 3 spindle and10 rpm.

EXAMPLE 14 One gram of the novel interpolymer of Example 1 was mixedwith 46.5 grams of distilled water, 1.4 grams 15 percent (w/w) sodiumhydroxide solution and 2.5 grams of sodium sulfate was prepared as inExample 13. The resultant mixture was found to have a Brookfieldviscosity of 6,400 CPS at 25 C using a No. 7 spindle and 10 rpm.

For purposes of comparison, the above mixture was prepared employing theunmodified PVM/MA copolymer of Example 1 in lieu of the novelinterpolymer of the instant invention. The resultant mixture was foundto have a Brookfield viscosity of 70 CPS at 25 C using a No. 3 spindleand 10 rpm.

EXAMPLE 15 One gram of the novel interpolymer of Example 1 was mixedwith 46.5 grams of distilled water, 1.4 grams 15 percent (w/w) sodiumhydroxide solution and 2.5 grams of sodium meta silicate. The mixturewas prepared as in Example 10 and found to have a Brookfield viscosityof 3,020 CPS at 25 C using a No. 6 spindle and 10 rpm.

For purposes of comparison the above mixture was prepared substitutingthe unmodified PVM/MA copolymer of Example 1 for the novel interpolymerof the instant invention. The resultant mixture was found to have aBrookfield viscosity of 98 CPS using a No. 3 spindle and 10 rpm.

EXAMPLE 16 One gram of the novel interpolymer of Example 1 was mixedwith 46.5 grams of distilled water, 1.4 grams of 15 percent (w/w) sodiumhydroxide and 2.5 grams of sodium carbonate according to the method ofExample 10. The mixture was found to have a Brookfield viscosity of2,520 CPS at 25 C using a No. 6 spindle and 10 rpm.

For purposes of comparison, the above composition was again preparedemploying the unmodified PVM/MA copolymer of Example 1 in lieu of thenovel interpolymer of the instant invention. The resultant mixture wasfound to have a Brookfield viscosity of l 10 CPS at 25 C using a No. 3spindle and 10 rpm.

EXAMPLE 17 One gram of the novel interpolymer of Example 1 was mixedwith 46.5 grams of distilled water, 1.4 grams of 15 percent (w/w) sodiumhydroxide solution and 2.5 grams of sodium acetate which was preparedaccording to the method of Example 13. The mixture was found to have aBrookfield viscosity of 5,600 CPS at 25 C using a No. 7 spindle and 10rpm.

For purposes of comparison, the above composition was again preparedemploying the unmodified PVM/MA copolymer of Example 1 in lieu of thenovel interpolymer of the instant invention. The resultant mixture wasfound to have a Brookfield viscosity of CPS at 25 C using a No. 3spindle and 10 rpm.

EXAMPLE 18 was found to have a Brookfield viscosity of 100 CPS at 25 Cusing a No. 3 spindle and 10 rpm.

EXAMPLE 19 4.0 grams of the novel interpolymer of Example 1 were mixedwith 48.0 grams of distilled water, 3.4 grams of 15 percent (w/w) sodiumhydroxide. 50.0 grams of double strength synthetic sea water comprising26.4 grams magnesium chloride .6H O, 3.84 grams calcium chloride .2l-lO, 9.6 grams sodium sulfate, 60 grams sodium chloride mixed to a totalof 1,200 mls. with distilled water were then added. The mixture wasrotated on the wheel of Example 4 for 48 hours and found to have aBrookfield viscosity of 63,600 CPS using a No. 7 spindle and 10 rpm.

For purposes of comparison the above mixture was again preparedemploying the unmodified PVM/MA copolymer of Example 1 in lieu of thenovel interpolymer of the instant invention. As a result of thisformulation, the polymer was found to separate out of solution.

EXAMPLE 20 1.0 grams of the novel interpolymer of Example 3 were mixedwith 24.0 grams of distilled water and 25.0 grams of 30 percent ammoniasolution. The mixture was then treated as in Example 4 and found to havea Brookfield viscosity of 220 CPS at 25 C using a No. 4 spindle and rpm.

As will readily be apparent from a review of the foregoing examples, thenovel interpolymers of the instant invention are particularly adaptedfor use as thickening agents in aqueous systems and, in particular, inaqueous systems having a high ionic strength.

Various modifications and variations of this invention will be obviousto a worker skilled in the art and it is understood that suchmodifications and variations are to be included within the purview ofthis application and the spirit and scope of the appended claims.

What is claimed is:

l. Interpolymers characterized by being uncrosslinked, water-soluble andconsisting essentially of the structural units in anhydride form:

wherein I Xrepresents N- -O;

R] Yrepresents OH,OR x

and when Y and R are taken together represent a single bond of an imidering; R and R represent hydrogen or the same or different hydrocarbonradicals having from 1 50 carbon atoms and together contain a total offrom 6 to 50 carbon atoms selected from the group consisting of normalchain alkyl, branched chain alkyl, cycloalkyl, and alkylaryl radicals(and where X= -O-, R does not exist); R represents the same or differenthydrocarbon radicals selected from the group consisting of methyl,ethyl, propyl, isopropyl, butyl, isobutyl, and -(CH CH O) (CH CHradicals wherein q represents an integer of from about 1 to about 3 andm represents an integer of from about 1 to about 3 wherein Unit I ispresent in an amount of from about to 99.5 mole and Unit II is presentin an amount of from about 25 to 0.5 mole 2. The interpolymer of claim 1wherein R is an alkyl radical having from six to 20 carbon atoms.

3. The interpolymer of claim 1 wherein X represents oxygen.

4. The interpolymer of claim 1 wherein X represents nitro en.

5. e interpolymer of claim 1 wherein R represents a methyl radical.

2. The interpolymer of claim 1 wherein R1 is an alkyl radical havingfrom six to 20 carbon atoms.
 3. The interpolymer of claim 1 wherein Xrepresents oxygen.
 4. The interpolymer of claim 1 wherein X representsnitrogen.
 5. The interpolymer of claim 1 wherein R3 represents a methylradical.